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1.
B. Culik A. J. Woakes D. Adelung R. P. Wilson N. R. Coria H. J. Spairani 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1990,160(1):61-70
Summary The energy requirements of Adélie penguin (Pygoscelis adeliae) chicks were analysed with respect to body mass (W, 0.145–3.35 kg, n=36) and various forms of activity (lying, standing, minor activity, locomotion, walking on a treadmill). Direct respirometry was used to measure O2 consumption (
) and CO2 production. Heart rate (HR, bpm) was recorded from the ECG obtained by both externally attached electrodes and implantable HR-transmitters. The parameters measured were not affected by hand-rearing of the chicks or by implanting transmitters. HR measured in the laboratory and in the field were comparable. Oxygen uptake ranged from
in lying chicks to
at maximal activity, RQ=0.76. Metabolic rate in small wild chicks (0.14–0.38 kg) was not affected by time of day, nor was their feeding frequency in the colony (Dec 20–21). Regressions of HR on
were highly significant (p< 0.0001) in transmitter implanted chicks (n=4), and two relationships are proposed for the pooled data, one for minor activities (
), and one for walking (
). Oxygen consumption, mass of the chick (2–3 kg), and duration of walking (T, s) were related as
, whereas mass-specific O2 consumption was related to walking speed (S, m·s-1) as
.Abbreviations
bpm
beats per minute
-
D
distance walked (m)
-
ECG
electrocardiogram
-
HR
heart rate (bpm)
-
ns
number of steps
-
RQ
respiratory quotient
-
S
walking speed (m·s-1)
-
T
time walked (s)
-
W
body mass (kg) 相似文献
2.
The interaction of solvated electrons with DNA results in various types of DNA lesions. The in vitro and in vivo sensitisation of DNA to -induced damage is achieved by incorporation of the electron-affinity radiosensitiser bromodeoxyuridine (BUdR) in place of
thymidine. However, in DNA duplexes containing single-stranded regions (bulged BUdR-DNA), the type of lesion is different
and the efficiency of damage is enhanced. In particular, DNA interstrand crosslinks (ICL) form at high efficiency in bulged
DNA but are not detectable in completely duplex DNA. Knowledge about the processes and interactions leading to these differences
is obscure. Previously, we addressed the problem by applying molecular modelling and molecular dynamics (MD) simulations to
a system of normal (BUdR·A)-DNA and a hydrated electron, where the excess electron was modelled as a localised eˉ(H2O)6 anionic cluster. The goal of the present study was to apply the same MD simulation to a wobble system, containing a pyrimidine–pyrimidine mismatched base pair, BUdR·T. The results show an overall dynamic pattern similar
to that of the motion around normal DNA. However, the number of configuration states when was particularly close to DNA is different. Moreover, in the (BUdR·T)-wobble DNA system, the electron frequently approaches
the brominated strand, including BUdR, which was not observed with the normal (BUdR·A)-DNA. The structure and exchange of
water at the sites of immobilisation near DNA were also characterised. The structural dynamics of the wobble DNA is prone to more extensive perturbations,
including frequent formation of cross-strand (cs) interatomic contacts. The structural deviations correlated with approaching DNA from the major groove side, with sodium ions trapped deep in the minor groove. Altogether, the obtained results
confirm and/or throw light on dynamic-structure determinants possibly responsible for the enhanced radiation damage of wobble
DNA.
Figure The structure of the tightly bound single water-layer between the DNA and the electron (Site-8, five H2O molecules, bold capped sticks); the rest of the “second” shell waters (lines, in atom type colour) surround the ˉ(H2O)6 cluster (yellow, space fill). Orange dashed lines H-bonds; only one of the five molecules from the single H2O layer mediates a single-step H-bond bridge with N7(A8); the other four present a network of two(three)-step H-bond bridges
between DNA/ partner atoms 相似文献
3.
A 3D QSAR analysis has been performed on a series of 67 benzodiazepine analogues reported as γ-secretase inhibitors using
molecular field analysis (MFA), with G/PLS to predict steric and electrostatic molecular field interaction for the activity.
The MFA study was carried out using a training set of 54 compounds. The predictive ability of model developed was assessed
using a test set of 13 compounds ( as high as 0.729). The analyzed MFA model has demonstrated a good fit, having r2 value of 0.858 and cross validated coefficient, value as 0.790. The analysis of the best MFA model provided insight into possible modification of the molecules for better
activity.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
4.
Effects of common soil anions and pH on the uptake and accumulation of perchlorate in lettuce 总被引:1,自引:0,他引:1
A mechanistic understanding of perchlorate () entry into plants is important for establishing the human health risk associated with consumption of contaminated produce
and for assessing the effectiveness of phytoremediation. To determine whether common soil anions affect uptake and accumulation in higher plants, a series of competition experiments using lettuce (Lactuca sativa L.) were conducted between (50 nM) and (4–12 mM), (1–10 mM), or Cl− (5–15 mM) in hydroponic solution. The effects of (0–5 mM) and pH (5.5–7.5) on uptake were also examined. Increasing in solution significantly reduced the amount of taken up by green leaf, butter head, and crisphead lettuces. Sulfate and Cl− had no significant effects on uptake in lettuce over the concentrations tested. Increasing pH significantly reduced the amount of taken up by crisphead and green leaf lettuces, whereas increasing significantly reduced uptake in butter head lettuce. The inhibition by across all lettuce genotypes suggests that may share an ion carrier with , and the decrease in uptake with increasing pH or provides macroscopic evidence for cotransport across the plasma membrane. 相似文献
5.
Micic Z Hahn V Bauer E Schön CC Melchinger AE 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2005,110(8):1490-1498
Midstalk rot caused by Sclerotinia sclerotiorum is an important disease of sunflower in its main areas of cultivation. The objectives of this study were to (1) verify quantitative trait loci (QTL) for midstalk-rot resistance found in F3 families of the NDBLOSsel × CM625 population in recombinant inbred lines (RIL) derived from the same cross; (2) re-estimate their position and genetic effects; (3) draw inferences about the predictive quality of QTL for midstalk-rot resistance identified in the F3 families as compared to those in the RIL. Phenotypic data for three resistance (leaf lesion, stem lesion, and speed of fungal growth) and two morphological traits (leaf length and leaf length with petiole) were obtained from 317 RIL following artificial infection in field experiments across two environments. For genotyping the 248 RIL, we selected 41 simple sequence repeat (SSR) markers based on their association with QTL for Sclerotinia midstalk-rot resistance in an earlier study. The resistance traits showed intermediate to high heritabilities
and were significantly correlated with each other
Genotypic correlations between F3 families and the RIL were highly significant and ranged between 0.50 for leaf length and 0.64 for stem lesion. For stem lesion, two genomic regions on linkage group (LG) 8 and LG16 explaining 26.5% of the genotypic variance for Sclerotinia midstalk-rot resistance were consistent across generations. For this trait, the genotypic correlation between the observed performance and its prediction based on QTL positions and effects in F3 families was surprisingly high
The genetic effects and predictive quality of these two QTL are promising for application in marker-assisted selection to Sclerotinia midstalk-rot resistance. 相似文献
6.
Christoph Kuhn 《Journal of biological physics》2006,32(6):563-572
A simple theoretical model of a Darwinian system (a periodic system with a multiplication phase and a selection phase) of
entities (initial form of polymer strand, primary mutant and satellite mutants) is given. First case: one mutant is considered.
One individual of the mutant appears in the multiplication phase of the first generation. The probabilities to find N individuals of the mutant after the multiplication phase M of the n-th generation (with probability δ of an error in the replication, where all possible errors are fatal errors) and after the following selection phase S (with probability β that one individual survives) are given iteratively. The evolutionary tree is evaluated. Averages from the distributions
and the probability of extinction are obtained. Second case: two mutants are considered (primary mutant and new form). One individual of the primary mutant
appears in the multiplication phase of the first generation. The probabilities to find N
p individuals of the primary mutant and N
m individuals of the new form after the multiplication phase M of the n-th generation (probability ɛ of an error in the replication of the primary mutant giving the new form) and after the following selection phase S (probabilities β
p and β
m that one individual each of the primary mutant and of the new form survives) are given iteratively. Again the evolutionary
tree is evaluated. Averages from the distributions are obtained.
The online version of the original article can be found at . 相似文献
7.
Factors affecting denitrification in agricultural headwater streams in Northeast Ohio,USA 总被引:2,自引:0,他引:2
As a result of increased anthropogenic nitrogen (N) loading in surface waters of agricultural watersheds, there is enhanced
interest to understand and quantify N removal mechanisms. Denitrification, an important N removal mechanism in aquatic systems,
may contribute to reducing N pollution in agricultural headwater streams. However, the key factors controlling this process
in lotic systems remain unclear. The objective of our study was to examine the factors regulating rates of denitrification
in the sediments of agricultural headwater streams in the mid-western USA. Denitrification rates were variable among streams
and treatments (<0.1–28.0 μg N g AFDM−1 h−1) and on average, were higher than those reported for similar headwater streams. Carbon quantity and quality, and pH had no
effect on denitrification, while temperature and nitrate (
) concentrations had a positive effect on rates of denitrification. Specifically, controlled denitrification following Michaelis-Menten kinetics. We calculated a value of km (1.0 mg -N L-1) that was comparable to other studies in aquatic sediments but was well below the median in-stream concentrations (5.2–17.4 mg -N L−1) observed at the study sites. Despite high rates of denitrification, this removal mechanism is most likely saturated in the agricultural headwater streams we examined, suggesting that these systems are not effective at removing
in-stream N.
Handling editor: D. Ryder 相似文献
8.
Microsomal prostaglandin E2 synthase (mPGES-1) has been identified recently as a novel target for treating pain and inflammation. The aim of this study
is to understand the binding affinities of reported inhibitors for mPGES-1 and further to design potential new mPGES-1 inhibitors.
3D-QSAR-CoMFA (comparative molecular field analysis) and CoMSIA (comparative molecular similarity indices analysis) - techniques
were employed on a series of indole derivatives that act as selective mPGES-1 inhibitors. The lowest energy conformer of the
most active compound obtained from systematic conformational search was used as a template for the alignment of 32 compounds.
The models obtained were used to predict the activities of the test set of eight compounds, and the predicted values were
in good agreement with the experimental results. The 3D-QSAR models derived from the training set of 24 compounds were all
statistically significant (CoMFA; q
2 = 0.89, r
2 = 0.95, , and CoMSIA; q
2 = 0.84, r
2 = 0.93, , ). Contour plots generated for the CoMFA and CoMSIA models reveal useful clues for improving the activity of mPGES-1 inhibitors.
In particular, substitutions of an electronegative fluorine atom or a bulky hydrophilic phenoxy group at the meta or para positions of the biphenyl rings might improve inhibitory activity. A plausible binding mode between the ligands and mPGES-1
is also proposed. 相似文献
9.
A. Robic D. Bertrand J.-F. Sassi Y. Lerat M. Lahaye 《Journal of applied phycology》2009,21(4):451-456
The water-soluble cell wall polysaccharides from green seaweeds of Ulva spp. (Ulvales, Chlorophyta), referred to as ulvan, demonstrate composition- and structure-related functional properties.
Mid-infrared spectroscopy combined with chemometric techniques was investigated as a means to rapidly predict the chemical
composition of ulvan extracts. A calibration was realized with 41 ulvan extracts from two Ulva species. The variables studied included the constituent sugars (rhamnose, xylose, glucose, galactose, glucuronic acid, iduronic
acid), protein, and sulfate contents. The correlation between Fourier transform infrared and chemical data was developed using
partial least squares (PLS) regression with full cross-validation (leave one out). The coefficients of determination in cross-validation
() and the standard error in cross-validation were determined for each variable. The PLS model validation resulted in a coefficient
of determination () and a standard error in prediction. Good predictions were obtained for rhamnose ( = 0.9244), xylose ( = 0.8758), glucuronic acid ( = 0.9415), and sulfate ( = 0.9218), which are the main ulvan constituents. However, minor components such as proteins, glucose, galactose, and iduronic
acid were not correctly predicted. This study showed that mid-infrared spectroscopy combined with PLS regression is a reliable
and fast method for the quantification of the main chemical constituents of ulvan extracts. 相似文献
10.
de Magalhães Erismann N Caruso Machado E Sant' Anna Tucci ML 《Photosynthesis research》2008,96(2):163-172
Photosynthetic limitations under moderate water deficit were evaluated in ‘Valência’ orange trees grafted on three different
rootstocks, in pots. Net CO2 assimilation rate (A
N), stomatal conductance (g
s), and photosystem II (PS II) operating efficiency (
) in response to changing intercellular CO2 partial pressure (C
i) were analyzed under controlled conditions. Drought decreased A
N and g
s, whereas remained unchanged. This resulted in a higher ratio between electron transport rate (ETR) and gross CO2 assimilation rate (A
G). Since the comparison of A
N–C
i gas exchange curves can lead to incorrect conclusions, a normalization of C
i values () of stressed leaves was applied. Then, the relationship established for irrigated trees between the ETR/A
G ratio and C
i was used to estimate the from ETR/A
G ratios measured under water stress. The response of A
N to suggests that the CO2 diffusional restriction is the main factor that limits photosynthesis in orange leaves under moderate water deficit. 相似文献
11.
Amino azobenzenes are important dyes in the food and textile industry but their application is limited due to their mutagenicity.
Computational modeling techniques were used to help understand the factors responsible for mutagenicity, and several quantitative
structure toxicity relationship (QSTR) models have been derived. HQSTR (hologram QSTR) analyses indicated that different substituents
at sites on both rings contribute to mutagenicity. Fragment parameters such as bond (B) and connectivity(C), as well as donor-acceptor
(DA)-based model provide significant results (q2 = 0.59, r2 = 0.92, ) explaining these harmful effect. HQSTR results indicated that a bulky group at ring “Y” and small group at ring “X” might
help to decrease mutagenicity. 3D-QSTR based on comparative molecular field analyses (CoMFA) and comparative molecular similarity
index analyses (CoMSIA) are also in agreement with HQSTR. The 3D QSTR studies reveal that steric and electrostatic field effects
have a strong relationship with mutagenicity (for CoMFA: q2 = 0.51, r2 = 0.95, and for CoMSIA: q2 = 0.51, r2 = 0.93 and ). In summary, negative groups and steric bulk at ring “Y” and small groups at carbon-3 of ring “X” might be helpful in reducing
the mutagenicity of azo dyes. 相似文献
12.
Marine invertebrate populations usually show high levels of genetic variability that has frequently been associated with spatial
and temporal environmental heterogeneity. One of the most heterogeneous marine environments is the intertidal zone, the habitat
of Collisella subrugosa, the most widespread and abundant Brazilian limpet. C. subrugosa has planktonic larvae that can disperse over long distances, what can promote gene flow among shores, working against interpopulational
differentiation. In this study we investigated the genetic variability and populational substructure of C. subrugosa through analysis of 24 allozyme loci in 14 samples (590 individuals) collected along 2,700 km of the Brazilian coast. The
genetic variability was high ( and ), as expected for intertidal species. Genetic differentiation among samples was low (F
ST = 0.03) what may reflect intensive gene flow associated with larval dispersal. However, we detected an isolation-by-distance
pattern of population substructure in one sampled region. High levels of heterozygote deficiency were also observed for many
loci in each sample. Alternative hypothesis are discussed, and the “breeding groups” is suggested to explain these pattern,
indicating the main cause as environmental heterogeneity. 相似文献
13.
Leaching losses of inorganic N and DOC following repeated drying and wetting of a spruce forest soil
Forest soils are frequently subjected to dry–wet cycles, but little is known about the effects of repeated drying and wetting
and wetting intensity on fluxes of , and DOC. Here, undisturbed soil columns consisting of organic horizons (O columns) and organic horizons plus mineral soil
(O + M columns) from a mature Norway spruce stand at the Fichtelgebirge; Germany, were repeatedly desiccated and subsequently
wetted by applying different amounts of water (8, 20 and 50 mm day−1) during the initial wetting phase. The constantly moist controls were not desiccated and received 4 mm day−1 during the entire wetting periods. Cumulative inorganic N fluxes of the control were 12.4 g N m−2 (O columns) and 11.4 g N m−2 (O + M columns) over 225 days. Repeated drying and wetting reduced cumulative and fluxes of the O columns by 47–60 and 76–85%, respectively. Increasing (0.6–1.1 g N m−2) and decreasing fluxes (7.6–9.6 g N m−2) indicate a reduction in net nitrification in the O + M columns. The negative effect of dry–wet cycles was attributed to
reduced net N mineralisation during both the desiccation and wetting periods. The soils subjected to dry–wet cycles were considerably
drier at the final wetting period, suggesting that hydrophobicity of soil organic matter may persist for weeks or even months.
Based on results from this study and from the literature we hypothesise that N mineralisation is mostly constrained by hydrophobicity
in spruce forests during the growing season. Wetting intensity did mostly not alter N and DOC concentrations and fluxes. Mean
DOC concentrations increased by the treatment from 45 mg l−1 to 61–77 mg l−1 in the O tlsbba columns and from 12 mg l−1 to 21–25 mg l−1 in the O + M columns. Spectroscopic properties of DOC from the O columns markedly differed within each wetting period, pointing
to enhanced release of rather easily decomposable substrates in the initial wetting phases and the release of more hardly
decomposable substrates in the final wetting phases. Our results suggest a small additional DOC input from organic horizons
to the mineral soil owing to drying and wetting. 相似文献
14.
Wu X Xiao W Liu C Chao L Qu C Chunxiang Q Huang H Hao H Liu X Xiaoqing L Chen L Liang C Su M Mingyu S Hong F Fashui H 《Biological trace element research》2008,121(3):258-265
Lead (Pb2+) is a well-known highly toxic element. The mechanisms of the Pb2+ toxicity are not well understood for nitrogen metabolism of higher plants. In this paper, we studied the effects of various
concentrations of PbCl2 on the nitrogen metabolism of growing spinach. The experimental results showed that Pb2+ treatments significantly decreased the nitrate nitrogen absorption and inhibited the activities of nitrate reductase, glutamate dehydrogenase, glutamine synthase, and glutamic–pyruvic
transaminase of spinach, and inhibited the synthesis of organic nitrogen compounds such as protein and chlorophyll. However,
Pb2+ treatments increased the accumulation of ammonium nitrogen in spinach cell. It implied that Pb2+ could inhibit inorganic nitrogen to be translated into organic nitrogen in spinach, thus led to the reduction in spinach
growth. 相似文献
15.
The data processing method of the turbidimetric bioassay of nisin was modified to facilitate its industrial application. The
influence of the initial indicator concentration was minimized by a redefined specific dose of the bacteriocin as the quotient
between the titer of the added bacteriocin and the initial population density of the indicator in the suspension. It was found
that d
c = 0.125 μg ml−1 was the critical dose of nisin that can cause a complete inhibition of the indicator, Pediococcus acidilactici UL5, with an initial OD of 0.135. To eliminate the interference of the cell debris, an equation, , exploiting d
c, was formulated to obtain the intrinsic survival proportion. The use of the specific dose of the bacteriocin and the intrinsic
survival proportion as parameters of the dose/response curve greatly enhanced its repeatability and feasibility. A dual-dosage
approach was developed to further simplify the conventional standard dose/response curve method. 相似文献
16.
The biosorption of metal ions (Cr+3,
, Cu+2, and Ni+2) on two algal blooms (designated HD-103 and HD-104) collected locally was investigated as a function of the initial metal
ion concentration. The main constituent of HD-103 is Cladophora sp., while Spirulina sp. is present significantly in the bloom HD-104. Algal biomass HD-103 exhibited the highest Cu+2 uptake capacity (819 mg/g). This bloom adsorbed Ni+2 (504 mg/g), Cr+3 (347 mg/g), and (168 mg/g). Maximum of Ni+2 (1108 mg/g) is taken by HD-104. This species takes up 306, 202, and 576 mg/g Cr+3, , and Cu+2, respectively. Equilibrium data fit very well to both the Langmuir and the Freundlich isotherm models. The sorption process
followed the Freundlich model better. Pseudo-first-order kinetic model could describe the kinetic data. Infrared (IR) spectroscopic
data were employed to identify the site(s) of bonding. It was found that phosphate and peptide moieties participate in the
metal uptake by bloom HD-103. In the case of bloom HD-104, carboxylate and phosphate are responsible for the metal uptake.
The role of protein in metal uptake by HD-103 was investigated using polyacrylamide gel electrophoresis. 相似文献
17.
Calcification, a process common to numerous marine taxa, has traditionally been considered to be a significant source of CO2 in tropical waters only. A number of relatively recent studies, however, have shown that significant amounts of CO2 are also produced in temperate waters, although none of these studies was carried out on rocky shores, which are considered
to be very productive systems. We compared the CO2 fluxes due to respiration and calcification in two temperate species, the cirripedes Chthamalus montagui and Elminius modestus. The population dynamics of both species were estimated at two sites during a 1-year experimental period in order to establish
mean organic (ash-free dry weight) and CaCO3 (dry shell weight) production. Based on these parameters, we estimated the CO2 fluxes due to respiration and calcification. CaCO3 production was estimated to be 481.0 and
at each site, representing 3.4 and respectively, of released CO2. These fluxes represent each 47% of the CO2 released as a result of respiration and calcification. The production of CaCO3 at the high-density site was: (1) among the highest values obtained for temperate organisms, and (2) comparable to the estimated
CO2 fluxes for coral reefs. As calcifying organisms are well represented in temperate ecosystems in terms of both density and
biomass, our results provide clear evidence that calcification of temperate organisms should not be underestimated. Additional
studies on other rocky shore taxa are needed before the relative importance of calcification in rocky intertidal carbon budgets
can be generalized. 相似文献
18.
Desulfovibrio vulgaris (strain Marburg) was grown on H2 and sulfate as sole energy source in a chemostat limited by the sulfate supply. The biomass concentration and the sulfate concentration in the culture were determined as a function of the dilution rate. From the data a K
S (saturation constant) for sulfate of 10 M, a max of 0.23 h–1, and a
of 13 g/mol were calculated. The organism was also grown in chemostat culture on H2 and sulfite, H2 and thiosulfate, and pyruvate (without sulfate).
was found to be 35 g/mol,
36 g/mol, and Y
pyr
max
10 g/mol. The growth yields are discussed with respect to ATP gains in dissimilatory sulfate reduction. 相似文献
19.
Summary A set of three-dimensional triple-resonance experiments is described which provide
,
,
and
coupling constants. The pulse sequences generate E.COSY-like multiplet patterns and comprise a magnetization transfer from
the amide proton to the α-proton or vice versa via the directly bound heteronuclei. For residues with the 1Hα spin resonating close to the H2O signal, a modified HNCA experiment can be employed to measure the vicinal 1HN,1Hα couplings. Ambiguities associated with the conversion of
values into ϕ-angle constraints for protein structure determination can be resolved with the knowledge of the heteronuclear
3J-couplings. In favourable cases, stereospecific assignments of glycine α-protons can be obtained by employing the experiments
described here in combination with NOE data. The methods are applied to flavodoxin from Desulfovibrio vulgaris. 相似文献
20.
A mechanical molecular rotation model for liquid crystal (LC) systems is employed to evaluate phase transition temperature
of fluorinated phenylbicyclohexane isomeric LC compounds. Results show that when a fluorine atom is substituted along the
molecular long axis, an LC molecule acquires high rotational speed and its rotation becomes stable, thereby resulting in a
better thermal stability of the nematic phase. A novel explanation is proposed for the behavior of the nematic-isotropic phase
of the LC system when a heavy atom is substituted along the molecular long axis.
Figure Molecular conformation of fluorinated bicyclohexylphenyl compounds. . The fluorine atoms are substituted in different positions 2, 3, 4, and 5 of the phenyl ring, respectively. The axis expresses
molecular long rotation axis. 相似文献